ECG features of microvolt T-wave alternans in coronary artery disease and long QT syndrome patients

T-wave alternans (TWA) is a marker of myocardial electrical instability. We compared ECG features of microvolt TWA in coronary artery disease (CAD) an d long QT syndrome (LQTS) patients. Method. The study populations consisted of 43 CAD and 39 LQTS patients. TWA was detected in resting Holter recordi ngs using the new correlation method (CM). After preprocessing to adjust fo r RR variability and respiratory modulation, CM was used to quantify TWA am plitude (A(CM)), duration (N-CM), and magnitude (MAG(CM); defined as the pr oduct of A(CM) and N-CM). Results. TWA was detected in 19 (44%) CAD and 17 (44%) LQTS patients. TWA was associated with longer RR intervals (P = 0.006 ) and had larger magnitudes (P = 0.067) in LQTS than CAD patients. The TWA was identified as transient (nonstationary) in 15 of 19 (79%) TWA-positive CAD patients, and in 8 of 17 (47%) TWA-positive LQTS patients (P = 0.047). Conclusions. The frequency of TWA detected with CM is similar in LQTS and C AD patients. TWA is larger in LQTS than in CAD patients, whereas TWA is mor e frequently transient (nonstationary) in LAD than LQTS patients. In LQTS p atients, but not in CAD patients, a longer RR is associated with TWA, indic ating different electrophysiologic mechanisms in the two pathologies.